The applicant in the present case has previously proposed such a CDMA signal waveform quality measuring method as disclosed in Japanese Patent Laid Open No. 173628/1998. FIG. 7 shows an example of power display of various channels as measured by the measuring method disclosed therein.
In FIG. 7, electric power W is plotted along the axis of ordinate, while channels CH are plotted along the axis of abscissa. In the example of FIG. 7, Walsh code length is set at “64” to permit connection of 64-channel lines, and a state is shown in which channels 0, 1, 3, 5, 7, 9, 11, 13 . . . 61, and 63 are generating signals.
In the example shown in FIG. 7 it is proposed to merely fix Walsh code length to “64” and measure the waveform quality of CDMA signal. As to Walsh length of CDMA signal presently in use in portable telephone, a standard which permits change-over to six lengths of 4, 8, 16, 63, and 128 is under consideration.
A band width is set in a transmission line by Walsh code length and a channel number is determined by Walsh code. FIG. 8 shows a relation between Walsh code length as diffusion code length and Walsh code as diffusion code. L=4, L=8, L=16, . . . shown in the left column represent Walsh lengths. At Walsh code length L=4, a predetermined band ΔF is divided into four and four channels of 0, 1, 2, 3 are allocated thereto. The channel numbers 0–3 of the four channels are given in terms of Walsh code numbers 0, 1, 2, and 3.
As is seen from FIG. 8, as Walsh code length becomes larger, the number of employable channels increases in a doubly increasing relation and an employable band width becomes narrower in decrements of ½. From this relation it will be seen that a short Walsh code length is allocated to a telephone set which handles a large volume of data to be transmitted, while a long Walsh code length is allocated to a telephone set which handles a small volume of data. In FIG. 8, Walsh code lengths 64 and 128 are omitted.
Thus, in the actual base station, a Walsh code length is selected from among six Walsh code lengths of L=4 to L=128 in accordance with the communication band width which the telephone set concerned requires, and a Walsh code not in use is selected and is used. Therefore, it is necessary to test whether all the channels in all the Walsh code lengths are in normal operation or not.
Therefore, also in the waveform quality measuring system it is necessary that the waveform quality be measured for all Walsh codes in all Walsh code lengths.
It is an object of the present invention to provide a CDMA signal waveform quality measuring system which, no matter which Walsh code length defined in the standard may be used in the issuance of CDMA signal, can determine the waveform quality of the signal.